Measuring system



NOV. 21, 1944. I A B WHlTE v 2,363,372

n I MEASURING SYSTEM Filed May 8, .1943

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my. N4.

ATTOR `mon examples. .v f :in Generally stated, it is: an object of my inven- Patented Nov. 21, 1944 A.

n yMEAsUnnm SYSTEMl Alfred .BQ :Wh-ite',VV Murrysville, MPea., 'assigner to Westinghouse Electric & Manufacturing Company,` East Pittsburgh;Pa.,Va-vcorporaton of I Pennsylvania i Application Mays, 1943,'seiai No. 486,234

.My invention,,relates,fgenerally, to measuring systems anda-ithas reference, in particulanto ,currents impulse measuring systems for measur- -ingthe values of` currentimpulsesl of short duration suchfas are used in resistance welding operationsofwhich spot and seam. welding are.co1n'r tionr to provide. a; current k.impulse measuring 4sy'stemorY device that `is/simple and inexpensive; t'o manufacture andis rugged aswell as easy to operate. vifs' `.;More specically,it,is anobject of my invention to .provider for measuring the effective value of one or more impulses of current, such' asgare' used in` resistance welding.' by producing voltages vhaving .diierent predetermined relationsto the values of theV current-impulses vand. balancing c predetermined rectied portions of ,.said voltages -by means of a bridge circuit using a directionall currentmeasuring' device, whereby the. portion -ofxone-voltage required to ,balance a-predetermined portion of the other is a measure of; thev value offagiven current impulse. r

It is also an object. of my invention torpr vide e for measuring-the eifective values oflcurrent im- -pulses rin a circuit independently of the number and duration thereof.

Anotherzobject of'the4 invention is'to provide for using azerovbalanceibridge type measuring --.-circuit for measuring the eiectivevaluesof current impulses of, relatively short durations in. a

weldingsystem. l

- fYetanother object of systemy in order tofdetermine the relative values oie-,the current impulsesfjf l 1A further object of.my invention is to provide 'for measuring'fthe'.effective values of impulses -rof' current having wave forms which are other `than sine waves, and are such as may be producedin welding circuits having heat control;v

' Other'objects' willin'fpartbe obvious, and Willr in part be described hereinafter. v

'- In practicingmy invention/in one of its is passed through substantially. linear and nonlinear impedances. used to applyfa variable portion of the voltage z dropv of 'one ofthe iin'pedances to ya yzero balance type'galvanometer circuit in lopposition.f to a Xed 'portion ofthe voltage drop of the other impedance; 'I'he `adjustable control means Yused.l

my invention is to ,proa Hvide 'forV balancing `,voltages produced in ,subf stantially linear and Jion-linear impedancesby relatively short impulsesI of current in al Welding forms, 'the currentto be measuredgora portion thereof,

Voltage divider: means are ment vof my invention as it may be applied toa I vto:balancetldeportions ofY these voltages` is calibrated to indicate the eiective value 4of the cur- `rentimpulses for which a balanced condition is obtained.

'Fora further understanding of the nature 1 and scope of my invention reference may be made to theffollowingdetailed description, which may vbe read in conjunction with Athe accompanying drawing., inwhhr f Figure lgisa diagrammatic view of one embodiresistance Welding system. f

Fig.v 2 shows-fanumber of curvesillustrating l the 'method of obtaining 'a 'balancent the current in an alternative form; .I `A`',-Fig. 4 is a diagrammatic yiewof another `emmeasuring system; c y l Fig. 3 is a diagrammatic view of. the invention bodiment 4of the` invention;

Fig.r shows a plurality. of curves illustrating the method-of obtainingl a balance in the circuit shown -in Fig. 4f; c

Fig. 6 is adiagrammaticlview of a current ini- -pulse measuring circuit embodying the invention ,25 7 is a partly sectioned v vview of Iaj'co/ntrol transformer such asy may be used in thevmeasuring circuit of Fig. 6; and y Figgrepresents calibrationcurvesof the curin another-of-itsforms;`

side elevational rent Vmeasuring system shown in Fig. v6. y

Referring to Fig. 1 thereference numeral I 0 .may denote, generally,v ya power system such as, l for example, a resistance welding system wherein a welding circuit Il, yincluding welding 'electransformer :I Q, may be connectedto a source of trodes l2 vfor engaging Work I3 and a'welding alternating current I5 by switch means IVG. The switch means I6 may be of any suitable typer comprising, for example, a pair of inversely connectedarcdischarge devices 20 vprovided with suitable timing means for ,controlling the frequencyfand duration of the periods of conductivity ofthe devices, and heat control means for controlling. the period of conductivity ofthe de- `vices in'eachfhalf cycle duringwhichtheyconduct. Since the timingand heat control means are Wellknown 1in the art, no particular details thereof Vneedvbe shown in this application and -they are 4therefore denoted, generally, b'y the numeral 22. The timing and heat control means may, for example'be of the types disclosed and described in PatentsNos. 2,275,948a nd'2,290,543 issued to J W.' Dawson on March 10' and July 2l,

, 1942, andassigned tothe assigneeof this applicaution.- v Y In order to provide for measuring the effective values of the diiferent impulses of welding current supplied tothe welding circuit Il by the switch means I6 under different operating conditions of` the timing and heat control means, current measuring circuit means 24 may be utilized, For example, a current transformer 25 may be used for providing a connection to the welding system l0 and producing a current proportional to the welding current but of a more `10 suitable value for measuring. In order to` produce a control voltage which has a predetermined relation to current impulses of different. values,v l circuit means 26 may be provided-The circuit, means 26 may, for example, have asubst'antial 15 ly linear relation to the values of the current im-r pulses in the welding circuit., Other` relations may be used, and a circuit could be used wherein the relation to the current impulsesl isv non-lin,y ear, the voltages being, for example, more than proportionately greater for greater values of impulses, varying'as the square thereof, for instance. The circuit 26 may comprise a transformer 21 having a primary Winding 28 for con nection to the current transformer 25 and Va sec- 325 ondary winding 29 disposed to be connected to a suitable voltage dividingv impedance such as the resistor 30 through rectifying means comprising a bridge circuit 32 of rectifier devices 33, The

transformer 21, resistor 30 and rectiflerpcircuit'30 32 may comprise the linear voltage circuit if desired, but in order to reduce the load on the rectifler circuit' 32, a substantially linear impedance, such as the variable resistance 35, may be connected across the secondary winding 29 of theX '35 transformer 21.

In order to provide a control voltage in response to impulses ofwelding current and varying in a different predetermined relation thereto, being, for example, substantially non-linear with respect to welding current impulses of different valuessubstantially constant, or at least less than proportionate values for increasing values of impulsescircuit means 36 may be provided comprising a control transformer '31 having a 4 primary winding 38 connected to the current transformer 25, in series circuit relation with the primary winding 28 of the transformer 21 and a secondary winding 39 connected to a suitable voltage dividing impedance 40 through a bridge circuit 4l of rectifier device 33.

In order to provide a voltage across the impedance 4l! which is substantially non-linear in relation to welding current impulses of different values, the transformer 31 may be operated at a UU sufficiently high flux density so that its core saturates at a relatively low value of current such as, for example, about 20% of the maximum current be measured. Above this value the output voltage of the transformer 31 will remain substantially 60 constant for different values of current impulses.

vIn order to utilize the voltages produced by the transformers 21 and 31 to indicate the values of the current impulses in the welding circuit, a measuring device such as the microammeter or galvanometer 42 `may be connected in bridged relation to the impedances 30 and 40 which are connected across the transformers 21 and 31, respectively, these impedances being so arranged that the voltages thereof are in opposed relation.` For example, one terminal of the measuring device 42 `may be connected by means of an adjustable tap 44 to the voltage dividing impedance 40 while the other terminal may be connected to the voltage dividing impedance 30 by means of 75 a sliding contact 45. A suitable scale 46 may be provided in connection with the sliding contact 45, which scale may be calibrated to indicate the values of the current impulses in the welding circuit. Means such as the switch 48 and control resistors 49 and 50 may be provided for varying the impedance in the circuit of the measurf ing device`42, so as to vary the sensitivity thereof.

portionately with the current input to the measuring circuitinv a manner such as shown by the solid curve cof Fig. 2. For any given connection of thefadjustabletap 44 to the tapped impedance y4l), the average voltage applied to the measuring device 42, thereby will vary with the current input to the measuring circuit in a manner such as 'measuring device from the impedance 40 by the given current impulse. At this point the measuring device shows no deflection when the given current is owing or when no current is flowing, `so that a zero balance is obtained, `For any other value of current impulse anotherpoint must be found on the impedance 30 for obtaining a balance, and the scale 46 may, therefore, be calibrated to read the current at which balance is obtained.

`Calibration of the impedance 30 may be reacle ily secured by energizing the'welding circuit with a succession of current impulses of known values or by otherwise applying a succession of current impulses to the measuring-circuit of known values and of predetermined wave shapes, so that for diierent values of current impulses, difierent balancing points may be found on the impedance 3D, and the impedance thus calibrated by' means of a measuring device such as a thermocouple meter which is capable of reading the effective values of a succession of current impulses.

When thus calibrated the measuring circuit 24 maybe readily used to give an accurate indication of the values of single impulses of' relatively short duration, to which the usual type of measuring device is unable to respond because of short duration thereof (one half cycle or less), a succession of relatively widely spaced current impulses or a succession of relatively closely spaced impulses, with equal facility. TheA voltage dividing impedance 40 may also =be used for measuring the values of current impulses and may be provided with a scale calibrated for that purpose. In this case a lower setting of the sliding Contact 45 should'be used, so as to give a iiatter curve, such as the curve a of Fig. 2, so that a wider range of intersections with different nonlinear curves may be obtained for balancing the circuit.

In order to improve theaccuracy of the measuring circuit when measuring tube-controlled currents which may depart from a sine Wave, suitable control means 5I may be provided. In the measuring circuit 24 the impedance drop across the transformer 21 is proportional to the average value of the current input. That across the transformer 31 is proportional to the average value of the rateof change of current up to satis obtained. f

.f inductancey 64,.the curve a in Fig. 2 may be made 'uration'ineach half cycle". When the welding :to `have approximately the same `slope Vfor'any current 'or l'input'currentimpulses 'contain harmonicsias'is usually thecase when arcdischarge -ldevices"arefused'to lcontrolthe welding current, the voltages of-the transformers 21 `and /31 ymay "vary according to the dotted curves a and b' of Figk"2f"due to the'feifects of the harmonics in the '"weldingcurrent. A calibration of the measuring circuit based on a 60 cycle sine Wave would, thereforefindicate current values ywhich are low. f One r'nethodh df correcting this effect usesl control- 'mear'1sf5'ly comprising aninductance 52'iand a resistor 53 connected inl'series circuit relation across :the primary windings-.ofthe transformers 21- and r31. This 'circuitprovidesa bypass'for a portion k*of thev fundamentalcurrent wave and thus decreasesthe-'fundamen'tal component of the cur- "rent wave inthe' measuring circuit, thereby decreasing the slope' 'of curve a and shifting the fcurvel/bfto -the 'right' morey in proportion for the f 'fundamental'than' for theharmonics.' By propyerly proportioning' the values of the inductance 52 and the resistor53, the calibration of the scale` 2'46 may therefore vbemade to indicate thevalue 4 ofvtheeifective current'regardless ofthe har-, 1 Im'onicsnormally found in tube-controlled. weldfing currents..`

Referring to Fig. 3-the reference numeral 54 -may denotesgenerally,v a measuring circuitwhich may beA used vfor measuring welding current i1r1.v pulses in a similar manner tothe measuring cir- 'cuit 24 of Fig. 1.` :Substantially linear and nonflinear circuts55 and` 56 lmaybe provided,l com- ,Iprising as hereinbefo're described,v non-saturatingandsaturating vcontrol transformers 21 anda..V

v31 yhaving primary windings v28 and 38, `respectively, connected to thefelding circuit orother circuit inwhich currentimpulses are to be measured, andsecond'arywindings 29 and 39 connected to bridgecircuits '32 and 4|, respectively;l

of rectifier device 33, lwhich may be connected in opposed relation. A tapped impedance device 40 v .maybe connected across theV rectifier circuit 4I, `:and a suitable tappedim'pedance 51 may be con- 'nected across'the terminals of the rectifier cir-,1,

vcuit 32;l Connection'of the measuring device 42 may be made by means of a tap 44 disposed to be .connected to one or vanother of'the taps on the impedancedevice 40 and a'sutable connector 58 A-whichf may be arranged for connection to one -org, another of the taps 59 on the impedancedevice 51. .Means such as the switch 48 and control're- :.sistors 49 and50 may be used asin'the circuit24 of Fig. '1 for .varying the `sensitivity of the measof' avariableimpedance shunting the measuring l'circuit or by` means of a" variable ratio `trans. Vformer 60having,.1for example, an adjustable tap 6|. Means such as the scale 62 may be provided in connection with the tap 6| for indicating.' the valuel ofthe current impulses for which balance In order to correct'the calibrationof thescale 62 for harmonicsin the welding current, means f. The circuits shown in Figs. vl and y ysaturating transformer 31 as the non-linear imvalue of Welding current containing thev harmonics .normally found therein. Likewise, vthe proper value of resistor65 will cause the curve b to be .approximately equivalent. for any givenv ef- `fective value of current vregardless ofthe harmonics commonly found therein.-

3 embody a pedance. :These circuits give quite satisfactory results in most instances, ythough the current indication may `not be exactly the same for Awelds of extremelyshort lduration such as one or two vferent welding times.

halfcycles or less, as for longer welds lastingi'or I several cycles or more. Corrections may be made ein thisyrespect by calibrating the scales for varues of heat control and used in conjunction with :such-as the inductance 64 and resistori65'may be provided in'connectionzwith the transformers 21 'and 31, respectively.- iWith the proper, valueiof the impedance y3i). In the system of Fig. Seither of the-impedances 51 or 40 could b`e calibrated for ycorrection lmay thus be obtained by introducing an air` gap in the coreof vthese transformers. This diliculty mayalso be overcome by using l other types of non-linear impedances such as, for example, a vnonlinear resistance (silicon carbide),an electric discharge device, or low pressure; gas discharge *.device. A `vacuum tube may `also be used as a, source of non-linearvoltage.

. Referring to Fig. l` the reference numeral 61 may denote, generally, a further modication of n bridged relation` across a parallel circuit comprising a resistor 1| having a linear `characteristic, and a parallel path comprising a nonlinear resistance 12 and a. substantially linearresistance 13 connected inl series circuit relation.

Means such asfthe adjustable impedance device 14 may be used for varying ther sensitivity of the measuring device 42. l y

Referring to Fig. 5 the curve .d represents thel waveform of the voltage across the vresistor 1|.

The lvoltage across the non-linearresistor 12 f maybe representedl by thedotted curve e.

order to balance the measuring .device 42,' the' vadjustable contactm'ember 15 of the resistor 1| may be moved so that the average value ofthe portion of the voltage between the ycontact member 15 and the com-mon 'connection 16 bewhich is represented by the solid curve f* i's-equal to the average value of the voltage Icurve re.v` For any vother value of current impulse adifferent point must be found on the resistor 1| to balance the portion. of the voltage thereof applied to the measuring device 42 against the voltage pro- Iny iduced, `by the non-linear resistor 12, ,since 'this resistor has a :more or less definite voltage drop.

`'Ihe resistor 1| may, therefore, be provided `with a `suitable scale 11 which `may be calibrated in terms of the impulse current input to the measuring circuit. "This circuit lgives basically `an vindication of the peak value of the current im- `vtransformers 8| and 82 and connected together in opposed relation. Means such as the voltage.4

dividing resistor 86 may be connected across the rectifier circuit '83 and provided with an adjustable tap 81 for providing an adjustable unidirectional voltage having a substantially linear relation to the value of the impulses to be measured. A' scal 88 may be provided in connection with the adjustable tap 81 for indicating the value of the current impulse to be measured.

In order to provide a voltage havinga different predetermined relationto the value of the impulse to `be measured, impedance means such as the junction type rectifier device 90 'may be connected across the bridge circuit 84 to `provide a substantially non-linearY voltage relative to'the value of the current impulse to be measured. Control resistors 9| and 92 may be connected in series circuit relation with the rectier device 90. The resistor 92 may be made adjustable by means of a tap 93 and used asa fine adjustment in Calibrating the circuit to measure effective values of current impulses. 'Decreasing the value of the resistor 92 would have a similar effect to decreasing an air gap in 'the magnetic circuit of the transformer 82.

The measuring device 42 may be connected in bridged relation across the resistor 9|, the non-linear rectifier device 90, and a portion of the resistor 86. for indicating whenl a balanced point is obtained. Means comprising, for example, a switch 4 8 and control resistors 49 and `50 may be connected in series circuit relation with the measuring device- 42 for varying the Vimpedance of the measuring device circuit so as to vary its sensitivity.

In order to vary the sensitivity of the measuring device 42 Without appreciably varying the effective resistance of the bridging circuit connected across the linear and non-linear impedances 86 and 90, an auxiliary control resistor 94 may be connected in shunt relation with the control resistors 49, 50 and the measuring device `02. The values of the resistors 94, 49, and 50 may be so selected that the resistance of the lpzalrallel bridging circuit remains substantially constant for diierent positions of the switch 48.` -The resistor 94 may, for example, be substanthe measuring circuit operates substantially the `same as -that described in `connection with Fig. 44 except that the impedance drop across the inductance device 91 lis proportional .to the rate of change of current :rather than to the change of current itself and a portion of this impedance drop, namely, `that across the resistor 9| is added to the'volta-ge drop across the non-linear resistor The leffect of this arrangement is to peak the average voltage wave of curve e of Fig. 5 more for a current wave `shape containing harmonics such as is usually the case with tube controlled welding currents. By'proper design, primarily of the ratio between the impedance'drops across the .resistor 96 and the inductance device 91 and between the voltage drop across the rectiiier device 90 and the resistor 9|, the scale 88 may be made to indicate the effective value ofthe current impulses very closely =for any wave shape commonly met in `Welding currents. This result is demonstrated by the curves shown in Fig. l8, where the curve vgfrepresents the Cycle sine wave .calibration curve of the measuring circuit 80, and the curve h is the calibration curve for 28% heat ccntrol-the `effective value of the delayed 'ring impulses being 28% of the eilective v60 cycle sine wavecurrent without delay. A similar effect to that produced b-y the inductance device 91 may be secured by connecting a capacitor 9,8 across the secondary winding of the control transformer 8| instead of using 'the .inductance device 91. The capacitor 98 tends to flatten the vol-tage curve f of Fig. 5, which gives a. .similar result `to that produced b-y the inductance-'device '91 which tends to peak the voltage curve e. The condenser 98 and inductance 91 ymay be used separately, vor together, if desired. In both cases an effective peaking of the non-linear voltage curve relative to the linear `voltage curve is secured.

' The inductance device 91 may be replaced by changing the design of the control transformer 82 so as to provide a relatively high magnetizing current. Referring -to Fig. 7 it will be seen that the `transformer 82 may be modie'd from the usual closed iron core type so as to comprise .a core Aof substantially E-shaped laminations 99 having air gaps therebetween. The air gaps may, for example, be spaced by means of suitable thicknesses vof insulating material |0I, vand the lamin-ations 99 secured together by clamp means |02, with the primary and secondary windings |03 and |04 secured firmly therebetween.

Before calibrating any of the .apparatus described in the above description, the apparatus may be adjusted to indicate the effective value of current Afor all form factors of current vfor which the apparatus is to be used. lThe necessary adjustments have been provided lfor and described inthe above description, and the apparatus described in 'connection with Fig. 6 may be taken as a typical example. Where the impedance 91 is obtained by introducing an air gap in the lcore `of transformer 82, this impedance may be varied by varying the air gap, thereby 'introducing a correction proportional tothe rate of change of current. Fine adjustments may be obtained by adjusting the value yof the control resistor 92.

The adjustments may be made at a current of about 40% lof the maximum value of current for which the apparatus is designed, i. e., at about tWo 'amperes 'for a live ampere measuring circuit current. The adjustment `may be 'made so that the :galvanometer or measuring device 42 indiestes balance at, tnevs'amepoint on medial-fora pure -60c`ycle sine wave `current and foi-a current:

Which-fhasbeenfreduced yto the samefeffective;l f

value from a pure' E50-cycle `sine Wave current of aboutfour times? that effective-value by delayed ringheat controllmeans such as the electronic heat'control.denotedgenerally by the numeral-22.

-An example of one lprocedure for-adjustment for harmonics is as follows: v-Set the lairgap-in the transformerat yan effective vtotal length ofapproximately` .020*.040-V inch.L Check `the scale.y

controlled'l impulse istoo high, more correction is.

l needed, and the air gap should be shortenedor' thevaluezofthe resistor 92 decreased.;a Check the scale reading'again andreadjust airk gap or.

either of the resistors Ellv or 92, andzso Von .until the readings are substantially the 'Same for4 both y currents. u i

mechanical and/or'thermal constants thereof: `v

Since the measuring circuit is of-ja directional zero `balanced type, accurate; indications lof fthe' values of the Welding current impulses 'maybe secured`v independently of the duration and num-- ber of impulses. A measuring device' embodying the features of myinvention'is inexpensive and relativelyr simple n to manufacture-` Itr may be easily appliedto welding machines already in` use and is simple to operate. Once it hasbeen calibratedon current impulses of predetermined` shape and value the operator merely needs to ad' just the .measuring circuitadjusting means'until y a balance is obtained, whereupon the value of the 'The yapparatus may now `be calibrated for the.

full currentrange. .Since the circuit of Fig. 6 has been compensated for form factor,i it may be calibratedon 60,-cycle current. Circuits not compensated, may be calibrated on a current having a 4form factor equivalent'to that of thecurrent to `rbe measured. The calibration should be made against another measuring device ofsimilar cur` rent rangewhich is designed to, or :which is of: a'type that will, read effective `values ofcurrent directly. A thermocouple type of meter is satis-A factory. The calibration :may be made ona continuous current (or aicurrent consisting of a continuous seriesof impulses) -sc thatthefeifect of the mechanical or thermal inertia'of the standard or test meter or measuring device is.elimi` inated. y l

lThe calibration` is made, by passing acurrent through the apparatus and the standard meter vor measuring device, adjusting the 'voltage dividing impedance 86 to bring the needle of the measuring :device to balance,fand-notingjthe position' of the V,standard meter or measuring device. Thisisrepeatedfor a number Ofdifferent values of vcurv rent. The scale Areadings-.may then. be plotted j hl represents thecalibration on-,al28% heat vcon-f trolled current impulse, wherein the current fiovv` the tap 81 of the4 voltage dividing impedance 86( Y y andthe effective value ofthe current as read on current impulsefor which vbalance is lobtained may be read from'the calibrated-scale, or, ifde-A sired,-the heat control or other current adjusting? means of the welding rcircuit Amay be adjusted to .obtain a zero balance of the measuring device after the measuring circuit adjusting vmeans of themeasuring device has been preset for a given value of current as ,determinedby its calibrated. scale. f f

. Since certain changesmay bemade from the above description and different vembodiments of the invention may be .made Without departing from the spiritor scope thereof, itis intended that all the matterycontained in the labove de-` scription ,and shown in the accompanyingdraw, ing shallbe considered as. illustrative andy not in a limiting sense. i i

. I.claim as my invention; Y -v y l-1. A Weld. current measuring system` comprising, a control circuit disposed tobe connected to a Welding'circuit for vproducing a control voltage varying in predetermined relation to differentvalues of weld current pulses, an additional con,- trol circuit disposed to be connected tothe Weld- .ing circuit for producing anothercontrol voltage varying in a different predetermined relation to said different values of weld current pulses, a

.measuring device, and circuit means connecting the" measuring device in bridging relation to the Was-limitedtol about 1/2 of eachhalf cycle so as tohave an effective 'value of about 28%. A While power. factor ofthe current to be meay sure'd isnot a critical factor, it should bey noted that resistance Welders operate ata relatively'low;

y power factor. The Wave shape'of heat-controlled curreniSon very high powerr factor is radically different from the wave shape on low povvery factors and would Vcontain `many more harmonics Which would probably. be lost incurrenttransfformers used in conjunctionv with the measuring apparatus, Therefore, the calibration of the apparatus should be made on a relatively lowpower factor-cl'irrent,l say, .3. to .5, suchy as obtained on panying drawing,l it will Abe ,apparent'that I'have provided@ a simple and effetilvelmarmer for control circuits vinopposed relation yincluding calibratedadjusting means 'for balancingy voltages,

from vthe control circuits appliedto the measure` ingdevice by a 'given pulse of weld current, Where bythe adjustment of the adjusting meansis a measure ofthe effective value .of said weld current' pulse. l y' r I v2. -Weldl Acurrent `rneasuring means comprising,

a directional measuring device', a controlcircuit disposed to be connected to a Welding circuit fory producing a control voltage of predetermined lpolarity varying .in predetermined relation vto Weld current pulses` of differentvalues, an addi# tional control vcircuit disposed to be connected to'fthe Welding circuit for producing ,a control voltage of4 4predetermined polarity ,varyingr in. a, differentV .predetermined .relation to said pulses of .weld current, circuit means `connecting the measuring device in bridgingrelation to the' con-y trolcircuits in opposed relation, and .adjustable impedance means connected *for balancing the voltages applied to the measuring device from 'the control circuits, said impedance means being calibratedin accordance withy current pulses of predetermined values, whereby .the adjustment thereof at which'the voltages applied to the mea-' 1 suring rdevice balance is a measure of the effec tive Valuel ofthe current'pulse. "Y, l' l 3.v Weld current measuringmeans comprising. a measuring device, circuit means producing substantially linear and non-linear voltages, respectively, in different portions of the circuit means in response to a pulse` vof current, circuit means connecting measuring device to the aforesaid means so as to apply portions of said voltages to the measuring device in opposed relation, and adjustable control means operable to vary the relative values of said portions of the voltages for different values of current pulses so as `to balance them against each other, said control means being calibrated on current impulses oi predetermined shapeand value to indicate the effective value of a current pulse for .which a balance condition is obtained.

4. A measuring system for measuring relatively widely spaced current pulses in a circuit comprising, circuit means including substantially linear and non-linear devices connected to the circuit to produce substantially linear and nonlinear voltages across said devices respectively in response to a pulse f current in the circuit, sensitive measuring means, circuit means connecting the measuring means 'to the control means to apply portions of said linear and nonlinear voltages to the measuring means in-opposed relation, and adjustable `control means operable to balance the voltages applied to the measuring means and calibrated on the basis of substantially continuous current impulses of predetermined Wave form to indicate the value of a current pulse by the adjustment of the adjusting means necessary to maintain a zero reading on the measuring means during the impulse.

5. A measuring system comprising, control circuit means disposed to be connected to an im-- pulse energized circuit for producing a nonlinear voltage comprising the resultant between opposedy unidirectional control voltages produced in different portions of the circuit means and varying in different relations for corresponding values of current, a sensitive directional current `balance them, and circuit means operableto vary the impedance of the measuring device circuit to vary the sensitivity of the measuring device.

6. A Zero balance weld current measuring system comprising, control means disposed to bey connected to a welding circuit for producing `a voltage varying in predetermined relation to pulses of welding current of different values, ad-

ditional control' means disposed to be connected to the Welding circuit for producingv a second,

voltage varying in a different predetermined relation to said pulses of Welding current', rectler means associated With'both of the control means for rec'tifying saidvoltages, a directional zero balance current measuring device, and voltage divider means connecting the control' means in opposed relation` with the measuring device in bridged relation thereto,`said voltage divider beingcalibrated on a substantially continuous current impulse basis whereby the calibration reading for zero reading on Athe measuring device during an impulse is a measure of the current impulse.

"l, A zero balance current Vimpulse measuring circuit comprising, a directional current measur- ,linear unidirectional voltage in response to a current impulse, means for producing an opposed substantially non-linear unidirectional voltage in response to said pulse of current, and adjustable voltage divider means' connecting the directional current measuring device lin bridged relation with said means to balance a portion of one voltage against a portion of the other, said divider means being `calibrated whereby the reading when the portions of the voltages are balanced is a measure of the current pulse for which the balance is obtained. f

8.v In a zero balance meter. circuit, in combination, transformer means disposed to be connected to a circuit energized by spaced impulses of elec-y trical energy for producing a Voltage substantially directly proportional to the energy impulse, saturable transformer means disposed to be connected to the circuit for producing a voltage of non-linear relation with the value of the energy impulse, means to rectify said voltages, circuit means connecting the rectier means with the voltages in opposed relation, a relatively sensitive directional current measuring device, and means connecting the current measuringA device to thecircuit means in bridged relation, said means being adjustable for balancing a portion of the voltage from one of the rectier means against a portion of the voltage from the other and calibrated, whereby the adjustment for balance is a measure of the energy impulse.

9. An impulse measuring circuit comprising, circuit means disposed to be connected to a circuit energized by current impulses of varying wave forms including a pair of impedance devices for producing opposed unidirectional voltages varying in different predetermined relations respectively for current impulses of different values, reactance means associated with said means for minimizing the effect 'of varying harmonic contents in current impulses of different wave form by effectively reducing the peak values of one of said voltages relative to the other, a galvanometer device, and circuit means connecting the galvanometer device in bridging relation vcurrent impulses of relatively short duration for producing a voltage having a substantially linear relation to the value of each current impulse, additional transformer means disposed to be connected to said circuit to produce avoltage havinga substantially non-linear relation to the value of each current impulse, means to lrectify said voltages, a directional' current measuring device, means including voltage dividing means connecting the'rectifler means in opposed rela-'- tionto the current measuring device for balancing a predetermined portion of one voltage against a variable portion of the other to indicate the value of the current impulsefor which the voltages balance.

' l1. A current impulse `measuring device for measuring current impulses of relatively short duration comprising, circuit means disposed to be connected to a circuit energized by current impulses of relatively short duration for producing a lunidirectional'volta-'geA proportional to` the value off each impulse, means' to` rectify said volt#- l spectively,

` age,separate impedance means connected to the rectifying means and disposed to produce substantially linear and non-linear voltage drops recurrent measuring means, circuit means connecting the current measuring means to the impedance means in bridging relation for applying opposed linear and non-linear voltages respectively thereto, and circuit means adjustable to vary the relative values of the linear and.

non-linear voltages applied to the measuring means so as to balance the linear and non-linear voltages against each other.

12. A zero balance type current measuring dervicefor measuring current impulses of relatively v connecting the current measuring instrument in bridged relation with the voltage divider means, said circuit means including adjustable connecting means for varying the point of connection to one of the voltage divider means for balancing the voltages applied to the current measuring inf strumen; to obtain a zero reading.

13. An impulse measuring device comprising, a pair of transformer means disposed to be connected to an impulse energized circuit, circuit means connected to the transformer means for producing separate substantially linear and substantially non-linear opposed unidirectional voltages, respectively, inresponse to current impulses y vn said circuit, means including a reactance `device connected to one of the circuit means for causing the voltage Wave of the non-linear voltt age to be more peakedr than that of the linear v voltage, directional current measuring means, and circuit means including an adjustable connection to one of the voltage circuits for connecting the current measuring means in bridged relation with said circuits and balancing the voltages applied thereto from the circuits.

y14. A current measuring system for measuring the value of current impulses of relatively short duration comprising, circuit means disposed to be connected to a circuit energized by curreni-I impulses of relatively short duration for producing opposed unidirectional voltages in different portions of said circuit means having substantially i linear and non-linear relations, respectively, to

the values of the current impulses, an inductance device. connected to the non-linear voltage circuit for increasing the non-linear wave peak relative to the linear Wave peak, a galvanometer, and circuit', meansv connecting the galvanometer in bridged relation to the circuit means including v'an adjustable connection to the linear circuit for `balancing a, portion Aof ythe non-linear circuit voltage therewith,

15. An impulse current measuring circuit com- |prising, circuit means disposed to be connected to a circuit energized by electrical impulses of relatively short duration and varying Wave form for producing separately substantially linear and non-linear voltages, respectively, in response to the impulses, galvanometer means, circuit means connecting the galvanometer means in bridging relation with the circuit means including an adjustable connection for balancing a portion of the linear -voltage against a portion of the nonlinear voltage, kand adjustable impedance means connected in series circuit relation with the galvaynometer means for varying the sensitivity thereof and provided with shunt impedance means for maintaining the net impedance of the bridging, A

circuit substantially constant.

. .16, A measuring system comprising, circuit means including means for Aproducing linear and non-linear voltages in diierent portions thereof in response to the quantity to be measured, a

condenserl connected to the circuit means for causing the non-linear voltage to be relatively more peaked by reducing the peak of the linear voltage, means to rectify the voltages, measuring means, and circuit means including an adjustable connection connecting the measuring means in. bridged relation to the circuit means so as toV apply portions of the' linear and non-linear voltages thereto in opposed relation.

B. WHITE. 

